Recently, electric devices such as refrigerators, etc., are provided with many sensors and actuators within them in order to meet the demand for a plurality of different and intricate functions. The schematic configuration of a conventional refrigerating and cooling device provided with a communication system will be explained below with reference to FIG. 46.
As shown in FIG. 46, the conventional refrigerating and cooling device is provided with a control section 501 on the upper part of the device. Further, the following output units (actuators) are provided within a refrigerating compartment 548, a cooling compartment 549, and a vegetable compartment 550, or outside a casing 536 in respective predetermined positions: a compressor 522 for supplying cold air into an evaporator (not shown); a heater 544 for removing frost adhering to the evaporator; an electrical fan 545 for circulating cold air generated from the evaporator into the compartments 548, 549, and 550; an electrically operated damper 546 provided along a cold air path between the refrigerating compartment 548 and the cooling compartment 549. Further, the refrigerating and cooling device is also provided with sensors such as thermistors 541, 542, and 543. Because the above output units are electrically connected to the respective control sections 501, most one to one, more than two wires 515 are provided for each output unit. The communication system is mainly composed of the control sections 501 and many wires 515. Additionally, the wires 515 and feeders 523 are provided on the back surface of the casing 536.
The control section 501 is provided with a power circuit 502, a microcomputer 503 which is an essential part of the control system, an input circuit 509 for receiving a signal from sensors, a drive circuit 510 in each output unit, a drive unit 511 for activating each of the above output units, a connector 540 for electrically connecting the wires 515, which are connected to each output unit, and the microcomputer 503, and other units. AC power is supplied from an AC power supply (not shown) to the power circuit 502 through the feeder 523. A part of the AC power supplied to the power circuit 502 is stepped down and rectified in the power circuit 502. Then, after being converted into DC power in the power circuit 502, it is supplied to each output unit through the drive circuit 510 and the drive unit 511. In the meantime, with a further stepdown, it is supplied to the microcomputer 503, etc.
Based on signals received from sensors through the input circuit 509, the microcomputer 503 controls each output unit through the drive circuit 510 and the drive unit 511 so as to adjust the respective temperatures in the compartments 548, 549, and 550.
However, in the above arrangement of conventional devices, because the output units and sensors are electrically and directly connected one to one to the respective control sections 501, the same number of I/O units as the number of output units and sensors are required in the microcomputer 503. Moreover, a large number of wires are required for connecting output units and sensors to the respective control sections 501, thereby presenting the problem of noise being generated in controlling the output units.
When a large number of wires 515 are required, for example, when manufacturing the refrigerating and cooling device, the process for routing the wires 515 becomes complicated, and a long time is required for the process. Moreover, when long wires (for example, with the length of over 100 m) are used, problems such as disconnection of the wires are likely to occur. The above arrangement also presents the problem of increases in the weight and the manufacturing cost of the device.
The wires 515 are normally provided in the heat insulating material provided between the casing 536 and an outer casing of the device. Therefore, in order to provide a large number of wires 515, the heat insulating material must be made thicker, thereby presenting the problem of, for example, reducing the volume efficiency in the refrigerating and cooling device.
When the electric devices such as refrigerating and cooling devices have been manufactured in the factory, the performance tests are required to check if each internal device in the main device performs properly. These performance tests require a long time in conventional models. For example, when the performance tests of the electric damper 546 are carried out to check if the electric damper 546 opens and closes properly, the temperature of the thermistor 542 must be dropped using a cooling agent. Thus, the performance test cannot be carried out easily. As described, in conventional models, carrying out the performance tests is a large burden to the workers, and a long time is required for the performance tests, thereby reducing the manufacturing efficiency.
When trouble has occurred in an electric device, such as a refrigerating and cooling device, in the user's place, in order to figure out the cause of the trouble, a serviceman carries out performance tests for input units, such as sensors, and output units, such as heaters. Conventionally, the serviceman disassembles the electric device for the performance tests. Therefore, the cause of trouble in the electric device cannot be figured out quickly in the user's place, and a long time is required for fixing the device, thereby hindering the serviceman from offering efficient services.
As shown in FIG. 47, some conventional refrigerating and cooling devices are arranged such that control information is transmitted and received among a main control section 601, a display control section 602, and an ice-making control section 603 through the communication lines 608 and 609. The display control section 602 is provided for controlling display on a display section (not shown). The ice-making substrate 603 is provided for controlling the operations in the ice-making compartment.
In order to connect the main control section 601 and the display control section 602, and to connect the main control section 601 and the ice-making control section 603, wiring materials are necessary. The wiring materials include the DC power feeder 605 and a earth conductor 606 for supplying power, a synchronization clock line 607, and a pair of communication lines 608 and 609. The communication processes between the main control section 601 and the display control section 602 are the same as the communication processes between the main control section 601 and the ice-making control section 603. Thus, only the communication processes between the main control section 601 and the display control section 602 will be explained below with reference to the timing chart of FIG. 48.
When the device is set in the test mode, one-way serial communications are carried out from the main control section 601 to the display control section 602 through the communication line 608 according to the timing shown in FIG. 48. On the other hand, in normal operations, one-way serial communications are carried out from the display control section 602 to the main control section 601 through the communication line 609 according to the timing shown in FIG. 48.
Here, it is assumed that the data transmitted from the display control section 602, which indicates the state of the switch include the following data of 4 bits each: datum 1 (0011), datum 2 (1010), and datum 3 (0110). When the data are transmitted from the display control section 602, first, the display control section 602 transmits a mark signal with a predetermined bit length, for example, a high level signal of 10 bits as a header. Then, the display control section 602 sends a low level signal of 1 bit as a start bit. Thereafter, the display control section 602 sends the datum 1 (0011), and datum (1100) obtained by reversing the datum 1 in this order. Similarly, the datum 2 (1010), and datum (0101) obtained by reversing the datum 2, the datum 3 (0110), and datum (1001) obtained by reversing the datum 3 are sent in this order, thereby terminating the transmission of the message. Immediately after completing the transmission of the message, the display control section 602 sends a mark signal, and repeats the transmission of the message in response to new data in the same manner as described above.
The main control section 601 receives the datum 1, the datum 2, and the datum 3 transmitted from the display control section 602 in this order, and analyzes the received data. Based on the received data, the main control section 601 controls the output units connected thereto through the wires 515 which respectively connect the above units.
The above conventional communication system is arranged such that one to one communications are carried out between the main control section 601 and each of the sections 602 and 603 to be controlled by the main control section 601. Therefore, if the number of the sections to be controlled by the main control section 601 increases, the numbers of the input and output ports for the main control section 601 and the communication lines are required to increase as well. Moreover, because a response message is not transmitted from the receiving end section in response to the message transmitted from the main control section 601, even if trouble has occurred while the message is being transmitted, and the message transmission cannot be carried out properly, it cannot cope with the situation. As a result, in the conventional communication system, a reliable control system cannot be achieved.